Fibrous dysplasia of mandible with chronic osteomyelitis in a child: report of one case.

We report here a 6-year-old girl with fibrous dysplasia (FD) of the mandibular bone. She had a growing mass with local pain over right chin after a severe trauma, which was thought to be chronic osteomyelitis (OM). After failure of antibiotic treatment, malignant bone tumor was suspected from imaging studies including magnetic resonance imaging (MRI). FD of the mandible with chronic OM was confirmed one year after its onset by repeated biopsy performed at our hospital. Causes of delayed diagnosis may include (1) FD of the mandibular bone and chronic OM have similar characteristics clinically and radiographically, (2) the previous biopsy was not performed at appropriate site, and (3) failure to include fibrous dysplasia in the differential diagnosis. In this report, we also review the features in radiology and MRI of OM and FD, which may help differentiate the diagnosis. When a patient with mandibular FD has acute symptoms, the possibility of superimposed OM or malignant change should be considered.